Relationship of specific gravity to sugar accumulation in stored Norgold and Russet Burbank potatoes

Studies were made on the influence of growing season and low fertility on reducing sugar accumulation in storage of the stem and bud portions of Russet Burbank and Norgold Russet potatoes separated into different specific gravity groups. The stem portion of Russet Burbank had a significantly different intercept and slope of regression line (between specific gravity and reducing sugar accumulation) than the bud portions of the same tubers indicating higher reducing sugar accumulation in the stem portion as well as differences in behavior as to amount accumulated at the different specific gravity levels. No significant difference in sugar content or behavior at the different specific gravity levels was obtained between stem and bud portions of Norgold Russet. Growing season did not cause significant differences in total sugar content or slope of the regression lines within the stem or bud portions of Russet Burbank. Low fertility level resulted in significantly higher sugar accumulation in the stem portion of Russet Burbank as compared to adequate fertility and there was also a trend toward less influence of specific gravity on sugar accumulation at the lower fertility level. Low specific gravity Russet Burbank potatoes tended to be more variable in sugar accumulation from year to year and also had wider differences in sugar accumulation between stem and bud portions than high specific gravity potatoes.     

Specific gravity,potato chip color and tuber mineral content as affected by soil moisture and harvest dates

In 1966 and 1967 the chipping quality of three potato varieties was studied using three moisture regumes, two nitrogen levels, and three harvest dates. Specific gravity and chip color of potatoes freshly harvested and of those stored 10 days, along with chip color differences between the two periods, were tested. Of the three varieties tested — Anoka, Kennebec, Irish Cobbler — Anoka§ specific gravity was least depressed by soil-moisture stress and its chip color least affected by time of chipping; all tubers, however, chipped darker after being stored. High soil temperatures were associated with low specific gravities and dark chips. In 1966 irrigation tended to lower soil temperature, resulting in lighter chip color for potatoes harvested from irrigated than from nonirrigated plots; also color was lighter at the first than at the later harvests. In 1967, when air temperatures were consistently lower and rainfall nearly adequate, chip color was lighter for potatoes harvester later in the season. Nitrogen levels did not influence chip color. Moisture regimes and varieties influenced mineral content of tubers more consistently for the two years than did harvest dates or nitrogen levels. Specific gravity did not correlate significantly with chip color.     

Some factors influencing the pH of apical and basal portions of Russet Burbank and Norgold Russet potatoes

Studies were made of pH changes of apical and basal portions of Russet Burbank and Norgold Russet potatoes during growth and in storage. Russet Burbank had a higher pH of the apical portion during the later stages of growth as compared to the basal portion. No significant differences between the two portions were found during growth with Norgold Russet. After a period of moisture stress the pH of the basal portion of Russet Burbank dropped significantly. The basal portion of both varieties at higher specific gravities had higher pH after storage than the apical portion. A highly significant negative correlation was obtained after storage between reducing sugar levels of tubers of different specific gravities and pH levels in both varieties. There were no significant differences in pH among storage temperatures of 34, 38, 42 and 45 F. However, the pH level at 48 F storage was significantly higher than at the other temperatures. The pH level of tubers from seedlings and varieties were poorly correlated with their reducing sugar contents after storage. It appears that pH can be an indicator of potential chip color only within the confined limits of a specific lot.     

Potato chip color,specific gravity and fertilization of potatoes with N−P−K

The effects of fertilizers on potato chip color were studied over a period of 11 years. Yield and specific gravity data also were taken. Single element and compete fertilizers were used in randomized block and split plot experiments. Most of the work was done with the Russet Burbank variety but in some experiments the Kennebec, White Rose, Norgold Russet and Cascade varieties were also included. Specific gravity and chip color data were taken immediately after harvest. Effects of storage and reconditioning on chip color were recorded in some cases. Though statistically significant effects of N?P?K on chip color were found, the differences were small and of no commercial importance. Neither nutrient balance nor total amount of fertilizer used greatly affected chip color whether the tubers were harvested “immature” in July or in October after the vines were dead. The greatest effect of over-fertilization was on the specific gravity of the tubers. As amount of fertilizer applied increased, specific gravity often decreased which would reduce the amount of processed product per unit of fresh produce. Since most manufacturers of processed potatoes prefer high specific gravity tubers perhaps varieties should be grown specifically for the processing industry. Since proper fertilization did not have a commercially important effect on chip color but greatly increased the yield, farmers should fertilize for maximum production when growing potatoes for potato chips.     

An investigation of the level of reducing sugars in diploid potatoes before and after cold storage

Summary The reducing sugar content and chip colour were studied in diploid potatoes bred for superior table and chipping quality. The reducing sugar content in the tubers of 119 diploid clones was estimated before and after cold storage (4–6°C) in the years 1987–1991, and reducing sugar and chip colour were determined in 1990 and 1991 for 36 clones. Thirty two clones had a significantly lower reducing sugar content after cold storage than cv. Mila. The year of evaluation, storage temperature and genotype significantly affected the reducing sugar content.     

Factors influencing reconditioning of Russet Burbank potatoes

Studies were made to determine factors which influence reconditioning of Russet Burbank tubers. Tubers from plants grown under low fertility were more difficult to recondition than tubers from plants adequately fertilized. Low specific gravity potatoes were also more difficult to recondition than high specific gravity potatoes even though the initial sugar content was approximately equal. The stem portion of Russet Burbank tubers lost considerably less sugars than the bud portion during the reconditioning process. It appears that factors which are responsible for high sugar development are also responsible for difficulty in sugar loss. Results also indicate greater difficulty in reconditioning early in the storage period with the loss of sugars becoming easier as the storage season progressed into spring.     

Internal quality of Russet Burbank potatoes following chilling

Russet Burbank potatoes were chilled at 25 F (?3.8 C), 27.5 F (?2.5 C), or 30 F (?1.1 C) for various periods of time and were then held at 45 F (7.2 C) for one or four weeks before testing. Susceptibility to injury was quite variable between the two crops and among tubers of the same lot exposed to the same treatment. The greatest amount of low temperature breakdown occurred in tubers chilled at 27.5 F (?2.5 C) for 10 hours. Flesh color, reducing sugar content, mealiness, and amount of sloughing in tubers that survived chilling were not markedly different from those in control samples although certain trends were observed indicating that the quality of chilled tubers was beginning to deteriorate. Chilling increased yellowness of flesh color in most treatments and darkness in several. Chilled tubers had a reducing sugar content slightly to moderately higher than the controls. They sloughed less than the controls and tended to be less mealy     

Influence of potato specific gravity on yield and oil content of chips

Tubers from bulk samples of Norchip potatoes were separated into specific gravity groups by weighing each tuber in air and then in water. Forty-nine chipping samples were assembled according to specific gravity from the segregated tubers (1.060 to 1.110 specific gravity). Chip yield increased and chip oil content decreased linearly through a specific gravity of 1.110. The contribution of specific gravity to chip yield was demonstrated by expressing chip yeild on a zero percent oil basis. For all lots of Norchips tested, the specific gravity distribution was similar, and all standard deviations (s) were the same (0.0064). Using s, a table of tolerances was compiled for estimation of the appropriate sample size for routine specific gravity determinations.

     

Sugar-end in Russet Burbank potatoes

Tissue selected from the stem- and bud-end of reconditioned tubers having sugar-end disorder was compared by color after frying and chemical composition to tissue removed from the two ends of tubers without sugar-end disorder taken directly from cold storage at 45 F, and after reconditioning 3 weeks at 70 F. Chemical analyses of selected tissue suggested that the dark finish-fry color at the stem-end of sugar-end tubers following reconditioning at 70 F was due to the inability of the physiological systems within the tissue to convert reducing sugars to starch and/or to use these sugars in the respiratory process. Of the components analyzed, only a high reducing sugar content was associated with a dark finish-fry color. Neither sucrose nor free amino acid content was associated with the sugar-end disorder. Extending the reconditioning period at 70 F for sugar-end tubers did not lower the reducing sugar content or the darkening of the stem-end tissue on frying.     

Reducing chilling injury of potatoes by intermittent warming

Potato tubers held continuously 19 weeks at 32 F developed chillinginjury symptoms early during storage and the symptoms worsened with time in storage. Early symptoms included browning and surface mold on skinned areas. By 11 weeks mahogany browning, blackheart, and hollow heart, bluish skin discoloration and sinking of intact skin were visible in daylight. And under ultraviolet light, yellow fluorescence was visible in halos, washes, or spots around or near internal tuber tissues discolored by other chilling-injury symptoms. Some damage at 32 F became visible after subsequent holding of tubers for 1 week at 60 F. Tubers accumulated high amounts of reducing and total sugar at 32 F and respiration, measured at 60 F as CO₂ evolved, was progressively stimulated by time at 32 F. Sugar build-up, respiration-rate increase, and chilling injury seemed to show no cause-and-effect relationship but appeared as separate phenomena each caused by the stress of holding tubers at too low a temperature. Moving potatoes to 60 F for 1 week after every 3rd week to interrupt storage at 32 practically eliminated all forms of chilling injury except skin browning and surface mold which were greatly reduced. Sugar content and respiration rates in tubers intermittently held at low and high temperatures were higher after periods in low temperature and lower after periods at 60 F, and in general were maintained at levels much lower than in potatoes held continuously at 32, 36, or 40 F. In all treatments sugar content was higher than desirable for chipping type potatoes. Holding potatoes at 60 F for 1 to 4 weeks before placing them at 32 F reduced skin browning and surface mold but had no effect on other forms of chilling injury, sugar accumulation, or respiration rates in tubers as measured after 15 to 19 weeks continuously at 32 F. Practically no chilling-injury symptom except for very little mold growth and browning of skinned areas developed in tubers held in 36 or 40 F.     

Effects of short periods of chilling and warming on potato sugar content and chipping quality

Two days of chilling (exposure to 1 C) had no detectable effect on chip color or sugar content of potato (Solanum tuberosum L.) tubers. Four days of chilling led to increases in sugars if potatoes were stored at 10 C or 19 C for 3 to 4 days after chilling ended. Longer chilling gave increases in sugars by the end of the chilling period, and returning tubers to 10 C or 19 C magnified the response. Glucose and fructose gave similar increases from chilling treatments, except that glucose levels were consistently greater. Sucrose was increased by chilling, but the response pattern did not always resemble that of the reducing sugars. Twenty-seven days of storage at 19 C after chilling lowered levels of reducing sugars late in the storage season but not in December. Cultivars differed in response to chilling. Kennebec tubers accumulated far more reducing sugars but much less sucrose than did Norchip tubers. Storage at 19 C after chilling lowered the sucrose content of Kennebec and Monona while raising that of Norchip.     

The effects of ozone and 1,8-cineole on sprouting,fry color and sugars of stored Russet Burbank potatoes

Ozone and 1,8-cineole were investigated as alternatives to isopropyl-n-(3-chloro-phenyl)carbamate (CIPC) to control sprout development of potato (Solatium tuberosum) tubers cv Russet Burbank during long-term storage. Sprout development was similar in ozone-treated and air-stored tubers, but both had much larger and more numerous sprouts than CIPC-treated tubers. Sucrose and reducing sugars in ozone-treated tubers were similar to levels in air-stored potatoes. Fry color was not different among potatoes stored in ozone, air and CIPC. Conversely, potatoes treated with 1,8-cineole did not produce any sprouts during the 25 week study. The fry color of tubers exposed to cineole was darker than either air-stored or CIPC-treated tubers. Sucrose and reducing sugar levels were higher in cineole-treated tubers than in tubers treated with CIPC.     

Correlations between quality parameters of potatoes during growth and long-term storage

The relationship between chip color, dry matter, sucrose, reducing sugars, ascorbic acid, protein, and storage temperature of commercially grown and stored Russet Burbank, Norchip, and Kennebec potatoes was investigated. Multiple correlation analysis of data, collected over a period of three years, demonstrated that while dry matter, reducing sugars, sucrose, and tuber weight were significant in determining chip color of freshly harvested potatoes, reducing sugars, tuber temperature, and sucrose were important in determining chip color of stored tubers. The relative importance of each parameter varied with the age of the tubers, year in which the potatoes were grown and stored, and cultivar. The multiple correlation coefficient among chip color, dry matter, sucrose, reducing sugars, and tuber weight was 0.901 for fresh Russet Burbank, 0.839 for fresh Norchip, 0.909 for fresh Kennebec, and 0.790 for the three cultivars combined. Similarly, the multiple correlation coefficient among chip color, reducing sugars, sucrose, and tuber temperature was 0.866 for stored Russet Burbank, 0.731 for stored Norchip, 0.914 for stored Kennebec and 0.790 for the combined stored material. Regression equations varied from cultivar to cultivar and from one season to another. This indicates that the quantitative relationship between the factors assayed was not sufficiently stable to serve as a general measure of prediction.     

马铃薯高淀粉生理基础的研究——块茎淀粉含量与糖的代谢

本试验以高淀粉品种晋薯2号、中淀粉品种内薯3号和低淀粉品种紫花白为试验材料,设置了小区试验,在生育期间从还原糖和可溶性糖的代谢与块茎淀粉含量积累变化的相关关系进行了研究,其结果:(1)块茎淀粉含量的积累变化与叶片可溶性糖含量变化呈显著正相关关系.因此,叶片可溶性糖含量可做为马铃薯高淀粉育种早期选择和品质预测的重要生理指标;(2)块茎淀粉含量积累变化与叶片还原糖含量变化呈正相关,故叶片还原糖含量亦可做为马铃薯高淀粉育种早期选择和品质预测的生理指标;(3)块茎淀粉含量积累变化与茎秆、块茎可溶性糖、还原糖含量变化相关性不强,但生育后期与茎秆可溶性糖含量呈显著正相关.     

Gamma irradiation of potatoes: Effects on sugar content,chip color,germination, greening,and susceptibility to mold

Russet Burbank potatoes that had been stored at 40°F. for 5 months after harvest were irradiated with 5,200 and 14,000 rad of Co⁶⁰ gamma rays. In general, irradiation caused an accumulation of sugars. At 40°F., the sucrose level rose to nearly 3 times that of the control in 16 days following irradiation. Fructose and glucose showed smaller increases and the latter did not accumulate significantly in the tubers given the higher dose of gamma rays. At 70°F., the levels of sucrose and glucose in the irradiated tubers rose above those in the controls, the difference reaching a maximum in 4 days and then declining. Irradiation had no effect on loss of fructose at this temperature. Color of potato chips processed from the irradiated potatoes was in general darker than that of chips from control tubers. The storage-time pattern of color change resembled that of the reducing rather than total sugar. Fourteen thousand rad did not prevent initiation of germination in the tubers but did destroy their sprout-growth apparatus. Although the lower dosage did not prevent initiation and subsequent growth, it prevented the formation of secondary tubers, which appeared on the sprouted control tubers. Furthermore, unlike the controls, the low-dosage potatoes developed branching hair sprouts with no tendency toward apical dominance during the early stages of sprouting. The rate of greening of gamma-irradiated and illuminated tubers was significantly less than that of unirradiated illuminated controls. Evidence is presented that irradiation may increase the susceptibility of potatoes to attack by molds under some conditions.     

Starch to sugar interconversion inSolanum tuberosum L. I. Influence of inorganic ions

No relationship could be found between calcium, magnesium, potassium, total phosphorous contents, and reducing sugar accumulation in apical and basal portions of Russet Burbank tubers. However, a highly significant positive correlation was found between inorganic phosphorous content of tubers and reducing sugar accumulation. Inorganic phosphorous and sugar levels were highest in the basal portion of moisture stressed and low temperature stored tubers, suggesting a relationship between inorganic phosphorous and enzymatic activity in the interconversion of starch to sugars in potatoes. Tubers stored at 5.5 C and 15.5 C had higher contents of calcium and magnesium in the basal portion and significantly higher potassium content in the apical portion. Storage temperatures or moisture stress during growth appeared to have no significant influence on calcium, magnesium, potassium or total phosphorus contents of the tubers.     

The relationship of chip color with structural parameters of starch

Seven potato cultivars (Norchip, Monona, Onaway, Snowden, Atlantic, Saginaw Gold, Novachip) and the seedling ND860-2 differing in their susceptibility to low temperature sweetening were analyzed to determine if starch structural stability parameters could be used to consistently predict and/or monitor chip color (Agtron score) of potatoes during storage at 4 and 12 C. Fresh tissue gelatinization temperature (Tp) was significantly correlated (P≤0.05) with chip color for all cultivars except Onaway, Snowden and Atlantic for tubers harvested in 1993 when stored at 12 C. No correlations existed between Tp of isolated starch and chip color (P>0.05). In 1994 no correlations existed between Tp of fresh tissue, Tp of starch and chip color at either 4 or 12 C (P>0.05). Prediction of chip color based on starch stability parameters was not possible. Starch crystallinity, amylose content and starch granule size distribution could not be used to predict or monitor chip color in stored tubers.     

An Economic Analysis of the Effects of Harvest Timing on Yield,Quality, and Processing Contract Price for three Potato Varieties

Harvesting potatoes at or near physiological maturity increases the likelihood of producing high quality tubers which contributes to producing high quality processed end-product. Some growers harvest earlier than recommended in order to meet contract requirements and supply processors with early potatoes. Early harvest impacts the incentive-adjusted price (IAP) and revenue even after an early harvest incentive is applied. This study utilized a typical frozen processor contract and compared the economic impact of harvest timing (early, normal, and late) on the IAP of three potato varieties: Russet Burbank, Clearwater Russet, and Alpine Russet, grown in field trials at Parma, Idaho during 2014 and 2015. Contract quality incentives included percent of tubers greater than 170 g, percent sugar ends, percent of U.S. No. 1’s, and specific gravity. When compared to normal or late harvest, early harvest resulted in a decrease in the IAP and overall profit due to a significant reduction in specific gravity. Early harvest incentive did not offset the loss of revenue with Russet Burbank, but did offset revenue loss with Clearwater Russet and Alpine Russet. Clearwater Russet and Alpine Russet had significantly lower sugar end scores than Russet Burbank. Clearwater Russet consistently produced higher specific gravities and Alpine Russet produced larger tubers compared to Russet Burbank. Clearwater Russet and Alpine Russet have agronomic characteristics that can provide an increase in IAP over Russet Burbank.     

Factors influencing time to breakdown (TTB) of cooked potato tissue

Cooking ability or time-to-breakdown (TTB) of different portions of potato tubers was determined by taking cores 1.27 cm (1/2inch) in diameter and 0.95 cm (3/8 inch) long from 12 locations in the tubers and cooking until penetration of a weighted rod pressing on the cores. Cores from the stem portion, on the average, required over twice as long for penetration of the rod during cooking as compared to cores from the bud section. The cores from the middle longitudinal portion of the tuber took longer to cook than cores from either side. Low specific gravity (1.070) tubers took significantly longer to cook than cores from high specific gravity (1.090) potatoes. However, when specific gravity of individual cores was determined with a pycnometer and TTB determined for the same samples, no relationships could be established. Cores from the stem portion took longer for TTB regardless of specific gravity or starch content. The data suggested much greater influence of cell wall structure as would be obtained from different portions of the tuber on TTB than starch content of the cells. No differences in TTB were obtained from tubers of high or low fertility or between Norgold Russet and Russet Burbank varieties, except Norgold was more uniform in cooking time between the stem and bud portion than Russet Burbank.     

Role of invertase in the accumulation of sugars in cold-stored potatoes

Freshly harvested potatoes contain low levels of total invertase and high levels of invertase inhibitor. Total invertase increases sharply when potatoes are placed in cold storage, but the inhibitor is not depleted in all varieties. The absence of basal invertase activity in Norchip tubers indicates that an excess of invertase is not required for reducing sugar formation. Analyses of 37 varieties and seedlings after 3 months cold storage revealed that the reducing sugar content is not proportional to the invertase activity. High sugar contents are associated with low inhibitor levels, but low sugars are not necessarily associated with high inhibitor levels. The results indicate that invertase participates in reducing sugar formation, but other factors are responsible for the regulation of starch-sugar conversion in potatoes during cold storage.